I've done this 2 times by complete accident. Here is the scenario. Reving through 2nd but shift to 1st instead of 3rd. [bang] Both times, the wheel hasn't locked up, and bike runs fine afterwards. Bike is S2R 800. I know it is bad to do this but is there any damage possible? Wouldn't I hear and feel it running different? Thanks.
No such thing as an over-rev on a desmo engine...
Your bike will blow up in a week. I'll give you a dollar for it ;D
Seriously, you would need to pull some tremendous RPM to do any harm to the engine, like maybe shifting down at redline. Even then it would probably survive.
doesn't the 800 have the APTC clutch? if so, that's what saved you.
Quote from: Raux on January 28, 2010, 08:14:28 PM
doesn't the 800 have the ATFP clutch? if so, that's what saved you.
APTC ;) yes it does. Does it really work? Apparently [thumbsup]
did you notice that was at 11pm :P
Yeah but doesn't the rev limiter take care of over revs? I've bounced off of it once while in first.
no it takes care of fueling. it's a fuel cut off, not a rev cutoff.
Quote from: bergdoerfer on January 29, 2010, 08:19:26 AM
Yeah but doesn't the rev limiter take care of over revs? I've bounced off of it once while in first.
If the over rev is due to the engine being driven by the rear wheel, due to a downshift at too high an RPM, no. The APTC clutch helps keep that from happening.
Quote from: bergdoerfer on January 29, 2010, 08:19:26 AM
Yeah but doesn't the rev limiter take care of over revs? I've bounced off of it once while in first.
The rev limiter will keep you from using the engine to pass the readline. On a bad downshift, the rear wheel can be driving the engine past the redline. The only way to prevent that is with mechanical intervention. Hence, slipper/APTC clutch. You got one.
As I understand it though, it is difficult to over-rev a desmo engine as you have mechanical valve closure instead of spring closure which should prevent the valves for getting thrashed by the piston. I imagine that you could do it if you really tried, but to do it accidentally by dropping a single gear would be a real challenge.
This is what I understood also. Just making sure. Thanks.
Quote from: yotogi on January 29, 2010, 10:26:48 AM
As I understand it though, it is difficult to over-rev a desmo engine as you have mechanical valve closure instead of spring closure which should prevent the valves for getting thrashed by the piston. I imagine that you could do it if you really tried, but to do it accidentally by dropping a single gear would be a real challenge.
Over rev is not all about the valves. it stresses the crank, piston and rods too. If it was all about the valves hitting the pistons, there would be no need for a rev limiter on a duc engine.
Personaly, I believe that everyone should hit their rev limiter at least once to know how the bike reacts. I was scared to death to find out, but once I did, it was no big deal. Some have said it feels as though the brakes are thrown on. Mine felt like I let off the throttle and just leaned forward a bit.
based upon some calculations and limits given by a noted Ducati Engine builder you can figure that the max theoretical rpm before things start flying apart for the 800 with the 66mm crank is about 11591rpm and the safe rpm is about 10500rpm
don't quote me on it (as my calculations may a be a little off) and i'm certain it depends on the build of the motor, valve specs, etc. as to whether you motor is capable and safe at those rpm's.
but those are specs for some race bikes i've been told.
the stock bikes obviously have a fuel cutoff way before that.
a cool thing for me, IF i keep the 57.2mm crank for the 696, are limits of 13375 and 12035 respectively.
Quote from: Raux on January 30, 2010, 10:28:40 AM
a cool thing for me, IF i keep the 57.2mm crank for the 696, are limits of 13375 and 12035 respectively.
Whoa... [evil]
I can only imagine what that would sound like!
have had the 900 way over what should be run, not worried about the valves, but the piston speed is what will cause problems. Had it up to high 10's on the manual tach.
Quote from: printman on January 31, 2010, 03:12:15 PM
have had the 900 way over what should be run, not worried about the valves, but the piston speed is what will cause problems. Had it up to high 10's on the manual tach.
safe operating range for the 68 crank is 10125 theoretical max is 11250 based upon piston speeds.
I mean no disrespect, but do you weigh like 400 pounds??
A couple of times i have downshifted from 2nd to 1st, thinking i was going 3rd to 2nd, at say 20 - 30mph and the back end has slid like i was locking up the coaster brake on my old bananna seat huffy.
I'm a hefty 220# and on an errant downshift the rear wheel slid. I've got the 800 Dark so no lsipper in my bike.
Generally the fuel cutoff will protect you on acceleration and either the slipper clutch or I would guess the limits of rear wheel traction would protect you on deceleration. Beyond that, over-revving briefly either way a few times shouldn't destroy anything unless you really get up in the revs. Even a little above the usual cutoff can sound like a banshee sqealing though. Don't worry, ride on ;)
Scott
i know there has been a lot of speculation about that APTC unit in the S2R800's... but i know for a fact that i LOVE mine, and it works VERY WELL.
Can you still get some decent engine braking with the APTC?
Scott
Quote from: scott_araujo on February 04, 2010, 11:17:45 AM
Can you still get some decent engine braking with the APTC?
Scott
yep.
it only kicks in when the wheel would lock up. which means you've done something wrong, and wouldn't be engine braking anyway... but rather sliding to your doom.
Quote from: corey on February 04, 2010, 12:09:04 PM
but rather sliding to your doom.
No, that's 'dynamic engine braking', an advanced technique not for the faint of heart. [laugh]
Scott
Quote from: corey on February 04, 2010, 12:09:04 PM
yep.
it only kicks in when the wheel would lock up. which means you've done something wrong, and wouldn't be engine braking anyway... but rather sliding to your doom.
The wheel will still lock up with that clutch. AMHIK...
Quote from: WhiteStripe on February 03, 2010, 04:57:07 AM
I mean no disrespect, but do you weigh like 400 pounds??
A couple of times i have downshifted from 2nd to 1st, thinking i was going 3rd to 2nd, at say 20 - 30mph and the back end has slid like i was locking up the coaster brake on my old bananna seat huffy.
Keep in Mind you don't have the APTC on your 1000.
Quote from: NAKID on February 04, 2010, 02:45:42 PM
The wheel will still lock up with that clutch. AMHIK...
most definitely. the APTC only forgives you to a point.
when it locks, it kinda skips... sorta like antilock brakes for engine braking.
it's wierd, i like it.